.burger {
    position: relative;
    height: 30px;
    width: 40px;
    cursor: pointer;
    display: block;
  }
  
  .burger span {
    display: block;
    position: absolute;
    height: 4px;
    width: 100%;
    // background: black;
    background-color: #fff;
    border-radius: 9px;
    opacity: 1;
    left: 0;
    transform: rotate(0deg);
    transition: .25s ease-in-out;
  }
  
  .burger .first-span {
    top: 0px;
    transform-origin: left center;
  }
  
  .burger .middle-span {
    top: 50%;
    transform: translateY(-50%);
    transform-origin: left center;
  }
  
  .burger .last-span {
    top: 100%;
    transform-origin: left center;
    transform: translateY(-100%);
  }
  
  .burger .first-span-active {
    transform: rotate(45deg);
    top: 10px;
    left: 0px;
  }
  
  .burger .middle-span-active {
    width: 0%;
    opacity: 0;
  }
  
  .burger .last-span-active {
    transform: rotate(-45deg);
    top: 10px;
    left: 0px;
  }